OCT Angiography and Cone Photoreceptor Imaging in Geographic Atrophy

Abstract

PurposeTo compare cone spacing and choriocapillaris (CC) perfusion adjacent to geographic atrophy (GA) in patients with age-related macular degeneration (AMD) and age-similar normal eyes.MethodsSubjects were imaged using adaptive optics scanning laser ophthalmoscopy (AOSLO), fundus autofluorescence (FAF), and swept-source optical coherence tomography angiography. The GA border was identified using FAF images; CC flow void was analyzed in 1° regions extending from the GA border. A grader masked to CC perfusion selected regions of interest (ROIs) with unambiguous cone mosaics in AOSLO images. At each ROI, cone spacing and CC flow void were converted to Z-scores (standard deviations from the mean of 12 normal eyes aged 50 to 81 years for cone spacing, and 60 normal eyes age 51 to 88 years for CC flow void).ResultsExcluding regions of GA and drusen, CC flow void in eight eyes of six patients with AMD was significantly greater than in four age-similar normal eyes (exact permutation test, P = 0.024). CC flow void was negatively correlated with distance from the GA margin (r = −0.35; 95% confidence interval [CI], −0.53 to −0.12). Increased cone spacing was significantly correlated with CC flow void (r = 0.33; 95% CI, 0.12 to 0.59). Cone spacing was increased in 39% of ROIs, while CC flow void was increased in 96% of ROIs.ConclusionsIn eyes with GA due to AMD, CC hypoperfusion was significantly correlated with, and more extensive than, cone photoreceptor loss. The results suggest that reduced CC perfusion contributes to the development of GA.

Optical Coherence Tomography-Angiography in Geographic Atrophy

“…Moreover, the area surrounding the GA margin was shown to reveal a significantly higher flow impairment compared to more eccentric areas in the same eye. These findings indicate that choriocapillaris degeneration may occur before the development of GA [30,31,[45][46][47][48]. Innovative adaptive optics investigations revealed that this choriocapillaris hypoperfusion even extended the region of increased cone spacing, an early sign of atrophic retinal processes [47].…”

“…These findings indicate that choriocapillaris degeneration may occur before the development of GA [30, 31, 45-48]. Innovative adaptive optics investigations revealed that this choriocapillaris hypoperfusion even extended the region of increased cone spacing, an early sign of atrophic retinal processes [47]. Thereby, choriocapillaris flow and structure might be potential therapeutic targets and/or susceptible early surrogate markers, possibly before the point of no return.…”

“…They could lead to a signal loss below the floater or the deposits and falsely appear as areas of non-perfusion [68]. Structural information may be used for partial signal compensation or for exclusion of respective areas as a more conservative approach [31, 47, 48]. However, most modern OCT-A devices take advantage of long-wavelength (>1,050 nm) laser light with increased tissue penetration and reduced signal attenuation from overlaying cells and extracellular material [34, 41].…”

Automatic Detection of Cone Photoreceptors With Fully Convolutional Networks

“…Understanding how the different models deal with this blur and the impact on performance should be considered in future studies. Also, future studies should evaluate the proposed method on datasets from pathological eyes, as many diseases can change the mosaic structure significantly,1–4 as well as with other imaging modalities such as dual split and confocal 24. Whether similar performance can be achieved with datasets from pathological eyes remains to be seen.…”

“…Specifically, these cells serve daylight and color vision. Diseases such as Stargardt's disease,1 retinitis pigmentosa,2 choroideremia,3 and macular degeneration4 are characterized by the loss of photoreceptors leading to impaired vision. A way to image the photoreceptor array is using an adaptive optics scanning laser ophthalmoscope (AOSLO).…”